Photolytic method of improving mercury capture in fossil (coal) fired systems

Abstract

A combustion-based system and related method includes a combustor for burning a combustible material, wherein an exhaust gas stream output by the combustor includes NO 2 and at least one metal including mercury. An ultraviolet light source is in optical communication with the exhaust gas stream. Ultraviolet light from the light source photochemically dissociates at least a portion of the NO 2 to form an NO 2 reduced exhaust stream. A sorbent containing filter media receives the NO 2 reduced exhaust stream and as a result of the reduction in NO 2 provides improved trapping efficiency of mercury.

1. A combustion-based system, comprising:
 a combustor for burning a combustible material, wherein an exhaust gas stream output by said combustor includes NO 2  and at least one metal including mercury;  
 at least one ultraviolet light source in optical communication with said exhaust gas stream, ultraviolet light from said light source photo-chemically dissociating at least a portion of said NO 2  to form an NO 2  reduced exhaust stream, and  
 a sorbent containing filter media for receiving said NO 2  reduced exhaust stream, said filter media trapping said at least one metal.  
 
     
     
       2. The system of  claim 1 , wherein said system comprises a fossil fuel fired power plant. 
     
     
       3. The system of  claim 1 , wherein said combustible material comprises coal. 
     
     
       4. The system of  claim 1 , wherein said system comprises a waste incinerator. 
     
     
       5. The system of  claim 1 , wherein said mercury in said exhaust stream is in the vapor phase. 
     
     
       6. The system of  claim 1 , further comprising a particle collection device for trapping said sorbent. 
     
     
       7. The system of  claim 1 , wherein said ultraviolet light source provides light in a wavelength range of 350 to 400 nm. 
     
     
       8. The system of  claim 1 , wherein said system reduces an amount of NO 2  in said exhaust gas to below 20 parts per million. 
     
     
       9. The system of  claim 1 , wherein said system reduces an amount of NO 2  in said exhaust gas to below 10 parts per million. 
     
     
       10. The system of  claim 1 , wherein said system is exclusive of catalyst particles. 
     
     
       11. The system of  claim 1 , wherein said sorbent media comprises activated carbon. 
     
     
       12. The system of  claim 1 , wherein said light source is disposed in said exhaust gas stream. 
     
     
       13. The system of  claim 1 , wherein said light source is disposed remote from said exhaust stream. 
     
     
       14. The system of  claim 13 , wherein a optical fiber network transmits said ultraviolet light to said exhaust stream. 
     
     
       15. The method of  claim 14 , wherein said ultraviolet light is in a wavelength range of 350 to 400 nm. 
     
     
       16. The method of  claim 14 , wherein said exhaust gas stream is generated by combusting coal. 
     
     
       17. A method for reducing mercury emissions from combustion-based systems, comprising the steps of:
 irradiating an exhaust gas stream including mercury and NO 2  with ultraviolet light, said light photo-chemically dissociating at least a portion of said NO 2  to form an NO 2  reduced gas stream, and  
 contacting said NO 2  reduced gas stream with a sorbent material, wherein said sorbent traps said mercury.